升级debian版本到 jessie

1.备份源，更新源内容到jessie ，/etc/apt/sources.list 内容deb http://mirrors.163.com/debian jessie main non-free contribdeb http://mirrors.163.com/debian jessie-proposed-updates main contrib non-freedeb-src http://mirrors.163.com/debian jessie main non-free contribdeb-src http://mirrors.163.com/debian jessie-proposed-updates main contrib non-freedeb http://mirrors.163.com/debian-security jessie/updates main contrib non-freedeb-src http://mirrors.163.com/debian-security jessie/updates main contrib non-freedeb http://http.us.debian.org/debian jessie main contrib non-freedeb http://security.debian.org jessie/updates main contrib non-free2.升级apt-get updateapt-get dist-upgrade3.查看版本cat /etc/debian_version
8.5
4.解决 The following packages have been kept back 问题